Heat-peelable pressure-sensitive adhesive sheets obtained by disposing, on a base material, a pressure-sensitive adhesive layer containing a blowing or expanding agent such as thermo-expandable microspheres are conventionally known (JP-B-50-13878, JP-B-51-24534, JP-A-56-61468, JP-A-56-61469, JP-A-60-252681, etc.). These heat-peelable pressure-sensitive adhesive sheets are developed to satisfy both adhesion and releasability after use. They are easily releasable from an adherend by heating to foam or expand the blowing agent, thereby lowering adhesion. By making use of such a feature, they have been used as a temporary supporting means upon production of electronic parts and as labels for goods to be recycled.
When the adherend is to be bonded at a relatively large area or is made of a material, such as metal, wettable with an adhesive (a material having a relatively high surface energy), releasability lowers, thereby sometimes making it difficult to maintain good releasability after heating.